Phase-shift circuits



Jan. 5, 1954 w. H. ELLIOT 2,665,407 PHASE-SHIFT CIRCUITS Filed Dec. 26, 1950 INVENTOR.

ATTURJVEY Patented Jan. 5, 1954 attain PHASE-SHIFT CIRCUITS William H. Elliot, Whitefish Bay, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application December 26, 1950, Serial No. 202,794

Claims.

This invention relates to electrical control systems and more particularly to phase-shift circuits which while not limited thereto are particularly advantageous for controlling gaseous discharge tubes in lamp dimming circuits.

A primary object of this invention is to provide adjustable phase-shift circuits capable of producing relatively large changes in the phase angle of an output voltage while maintaining the magnitude of such voltage relatively constant.

Another object is to provide phase-shift circuits of the aforementioned character which are responsive to the magnitude of an A. C. signal voltage.

Another object is to provide a phase-shift circuit of the aforementioned character which is responsive only to the A. C. signal voltage of greatest magnitude Where more than one such signal voltage is applied, and

A still further object is to provide a control system for lamp dimming wherein a phase-shift circuit of the aforementioned character is utilized for controlling a gaseous discharge tube in such a manner that lamp dimming characteristics of a preferred form are obtained.

Other objects and advantages of the invention will hereinafter be apparent.

The accompanying drawing illustrates preferred embodiments of the invention which will now be described in detail, it being understood that such embodiments are susceptible of various modifications without departing from the scope of the appended claims.

In the drawings:

Figure l is a diagrammatic showing of a control system for controlling the illumination intensity of incandescent lamps, and

Fig. 2 is a modified form of the system shown in Fig. 1.

Referring to Fig. 1, it shows a plurality of incandescent lamps 5 connected in parallel to buses B and 1.

Bus 6 is connector to supply line L of a single phase alternating current source and bus 1' is connected to line L of said source in series with the primary winding 8 of a transformer 8 having a secondary or control winding 8 Winding 8 of transformer 8 is connected at one end to the cathode b of a gaseous electron discharge tube 9 and at its other to the anode 9 of tube 9. Tube 9 is provided with a control grid 9 which is connected to cathode 9 in series with a resistor Ill and a secondary winding li of a transformer I I which has a primary winding l l Control grid 9 is also connected to cathode 9 in series with a capacitor l 2.

The part of the control system thus far described is of known form and it will be appreciated that the intensity of illumination of the lamps 5 is controllable by variation in the impedance of winding 8 of transformer 8. The impedance of winding 3 is controlled by variation in the current flowing in the winding S of the transformer as a function of conduction of tube 9 during its conducting half cycles. The conduction of tube 9 is controlled by varying the phase angle of the potential to which primary winding li of transformer II is subjected. The part of the control system now to be described comprises a phase-shift network for supplying and adjusting the phase angle of the voltage applied across Winding I I of transformer I I.

A transformer I3 has a primary winding it connected across lines L and L and a centertapped secondary winding I 3* which is connected at its lower end terminal to line L and at its upper end terminal to a bus 34. A voltage divider l5 has a resistance element i5 which is com nected at lower end to line L and at its upper end to bus I l and is provided with an adjustable tap I5 Tap I5 is connected to line L in series with a half-wave rectifier I6, primary winding I'I of a transformer H, which has a secondary winding I'I Winding II is connected at one end to bus l4 and at its other end to center-tap terminal I3 of Winding l3 of transformer E3 in series with secondary winding ll' of transformer I1. An adjustable resistor I8 and a capacitor are connected in parallel or shunt across secondary winding II The behavior and operation of the phase-shiit network will now be described.

Let it be assumed that rectifier E5 is omitted from the circuit and that winding Ii is directly connected to tap IE' of voltage divider I5. Further, let it be assumed that resistor i8 and capacitor I9 are omitted from the circuit. With this assumed circuit arrangement it will be apparent that when tap I5 is positioned on resistance element I5 at the lower end of the lotter, winding I'I Will be unenergized and consequently no voltage will be induced in winding ii of transformer I'I. Hence, the voltage across winding II of transformer II will be approximately of the same magnitude and in phase with the voltage across the portion of winding I 3 from center-tap terminal I3 to the upper end thereof.

Under the same assumed circuit arrangement and with tap I5 positioned at the midpoint of resistance element I 5 the voltage across winding I'i will be equal to approximately half the value of the voltage between line L and bus it,

or equal to half the voltage acros winding I? of transformer l3. Assuming further that the windings {i and li of transformer ll have approximately the same number of turns and that the connections to winding ll are so made that the voltage across winding li is in opposition to that across winding is then the voltage across winding il will efiectively cancel that across the portion of winding iii from center-tap 13 to bus it so that there will then be zero voltage across winding H If tap He is then moved to the upper end of resistance element ifi the voltage across winding H will be equal to twice that from the center tap IS to bus i i, and being in opposition to the voltage across winding 13* will apply a voltage across winding li equal in magnitude to half that across winding l3 and in phase opposition thereto. It will be seen with this assumed circuit arrangement that in moving tap it from the lower end to the upper end of resistance element us it is possible to eifect an approximately 180 phase shift of the voltage applied across winding li However, this assumed circuit arrangement has a defect in that the voltage applied across winding li drops to unacceptably low magnitudes for control purposes as tap l5 is positioned on resistance element ifi in the midportions thereof.

It has been found that with the circuit of Fig. l as actually constituted with rectifier I6 included in circuit between tap 15 and winding H and with adjustable resistor l8 and capacitor is connected in shunt across winding li it is possible to efiect shift in the phase of the voltage applied across winding I l through a wide angular range without attendant excessive drop in scalar magnitude of such voltage when tap 15 of voltage divider i5 is moved from one end to the other of resistance element I5 With proper selection of the values for adjustable resistor is and capacitor Hi, the voltages induced in winding li of transformer H will be of such magnitude and phasal relationship as to providea wide range of control for the tube 9.

Fig. 2 discloses a circuit which in certain respects is similar to that shown in Fig. l but has additional refinements, principally in its phaseshift network, which makes it particularly desirable for lamp dimming applications. The portions of the circuit of Fig. 2 which are the same as that of Fig. I bear the same reference numerals and only portions that are different will now be described in detail.

In the circuit of Fig. 2, the lamps 5 are connected in parallel to buses '6 and i and bus 6 is connected to line L while bus i is connected to a bus 25, which is connected to the overhanging end terminal 2% of an autotransformer 26 in series with winding 8 of transformer 8. Autotransformer 2s is connected through its end terminal 26* to line L and through its intermediate terminal 28 to line L The autotransformer 26 is utilized as a booster transformer for raising the lamp supply voltage above that available between supply lines L and L a sufiicient amount to compensate for the drop through winding 8 of transformer 8 occasioned by the normal impedance drop and the effect of the voltage drop across tube 9.

In place of the transformer 93 of the circuit of Fig. l a transformer 27 is used. Transformer 2? is provided with a primary winding 2! connected across lines L and L and with a secondary winding 2'1 having two intermediate tap terminals 27 and 21 Winding 27 is connected through its upper end terminal to bus i i and through its lower end terminal to line L in series with primary winding ll of transformer ii, control winding 28 of a saturable reactor 23, and an adjustable resistor 29. Intermediate tap terminal 27 of winding 22's" is connected to the lower end terminal of primary winding ti and intermediate tap terminal 22 is connected to the point common to the connection between upper end terminal of winding Ei and bus H3 in series with secondary winding [l of transformer ii, A. C. windings 28 and 28 of reactor 28, primary wind ing ll of transformer ii and capacitor 3d. Adjustable resistor 18 and capacitor is are connected in parallel or shunt with winding i'i The voltage divider i5 and rectifier is combination of the circuit of Fig. l are replaced by two such voltage dividers-rectifier combinations in the circuit of Fig. 2. One voltage divider 3% has its resistance element 3 i connected between line L and bus l5 and has its adjustable tap 3! connected to the upper end terminal of winding li of transformer H in series with a half-Wave rectifier 32. The other voltage divider 33 has its resistance element 33* connected across line L and bus I iand its adjustable tap 33 connected to the upper end terminal of Winding li in series with a half-wave rectifier 3 5. When two or more such voltage dividers are connected as shown in Fig. 2, the eifective signal applied to the phaseshift network is obtained from the voltage divider whose adjustable tap is positioned closest to the upper end of its associated resistance element, i. e., the highest A. C. signal dominates. Lower voltage signals from the other Voltage dividers have no appreciable effect on lamp voltage.

Capacitor 3t improves the transient stability of the phase-shift network, while saturable reactor 28 widens the range of possible phase-shift for a given change in A. C. signal voltage. Adjustable resistor 29 permits adjustment of the effectiveness of saturable reactor 28 since its adjustment determines the degree of saturation of such reactor and hence its impedance for a given A. 0. signal voltage.

With the phase-shift network of Fig. 2, phaseshift control of the gaseous discharge tube 9 may be obtained to provide adjustment of the intensity of illumination of lamps, such as the lamps 5, from blackout to full brilliance. The utilization of the transformer 21 with its overhanging section in its secondary winding 27* between intermediate ta terminal 2? and its lower end terminal provides that the change in lamp voltage will be substantially directly proportional to the change in magnitude of the A. C. signal voltage throughout the range of signal voltage adjustment.

I claim:

1. For supplying and effecting adjustment of the phase angle of a voltage applied to a control circuit, a network comprising a transformer having a primary winding to be supplied from an alternating current source and having a secondary winding with at least one intermediate tap,

a saturable reactor, a second transformer having a primary winding in circuit with the secondary winding of the first mentioned transformer and the control winding of said reactor and having a secondary winding in circuit with one intermediate tap of the secondary winding of said first mentioned transformer and the alternating current windings of said reactor, a resistor con-- nected in parallel with the secondary winding of said second transformer, a plurality of half-wave rectifiers, and a corresponding number of adjustable voltage dividers each of which has a resistance element connected in parallel with the secondary winding of said first mentioned transformer and an adjusting element connected in series with an associated rectifier to the corn nection between the primary winding of said second transformer and the control winding of said reactor, said network being adjusted in accordance with the adjustment of the voltage divider whose adjusting element affords the highest signal voltage.

2. For supplying and effecting adjustment of the phase angle of a voltage applied to a control circuit, a network comprising a transformer having a primary winding to be supplied from an alternating current source and having a secondary winding with two intermediate taps and an overhanging section between one of such taps and one end terminal thereof, a saturable reactor, an adjustable resistor, a second transformer having a primary winding in circuit with said one end terminal of the secondary winding of the first mentioned transformer, the control winding of said reactor and said adjustable resister and having a secondary winding in circuit with the other intermediate tap of the secondary winding of said first mentioned transformer and the alternating current windings of said reactor, a resistor and a capacitor connected in series and together in parallel with the secondary winding of said second transformer, a plurality of half-wave rectifiers, and a corresponding number of adjustable voltage dividers each of which has a resistance element connected in parallel with the secondary winding of said first mentioned transformer and an adjustable tap connected in series with an associated rectifier to the connection between the primary winding of said second transformer and the control winding of said reactor, said network being adjusted in accordance with the adjustment of the voltage divider whose tap affords the highest signal voltage.

3. In combination, a source of single phase alternating current, an output element, and an adjustable phase-shift network comprising a transformer having a primary winding connected to said source and having a secondary winding with at least one intermediate tap, an adjustable voltage divider having a resistance element connected in parallel with the secondary winding of said transformer, a half-wave rectifier, a second transformer having a primary winding connected to said source and to the adjusting element of said voltage divider through said rectifier and having a secondary winding in circuit with one intermediate tap of the secondary winding of the first mentioned transformer, said output element and said resistance element of said voltage divider and a resistor and at capacitor connected in series and together in parallel with the secondary winding of said second transformer.

a. In combination, a source of single phase alternating current, an output element, and an adjustable phase-shift network comprising a transformer supplied from said source and having a secondary winding with at least one intermediate tap connected to one side of said source, a half-wave rectifier, an adjustable voltage divider having a resistance element connected to said one side of said source in parallel with said secondary winding of said transformer, a second alternating current, an

transformer having a primary winding connected to said one side of said source and to the adjusting element of said voltage divider through said rectifier and having a secondary winding connected at one end to one intermediate tap of the secondary winding of said first mentioned transformer and at its other end to the connection between the resistance element of said voltage divider and said secondary winding of said first mentioned transformer in series with said output device and a resistor and a capacitor connected in series and together in parallel with the secondary winding of said second transformer.

5. In combination, a source of single phase alternating current, an output device, and an adjustable phase-shift network comprising a transformer having a primary winding connected to said source and having a secondary winding with at least one intermediate tap, a saturable reactor, a second transformer having a primary winding in circuit with the secondary winding of the first mentioned transformer and the control winding of said reactor and having a secondary winding in circuit with one inter mediate tap of the secondary winding of said first mentioned transformer, the alternating current windings of said reactor and said output device, a resistor and a capacitor connected in series and together in parallel with the secondary winding of said second transformer, a plurality of half-wave rectifiers and a corresponding number of voltage dividers each of which has a resistance element connected in parallel with the secondary winding of said second transformer and an adjusting element connected in series with an associated rectifier to the connection between the secondary winding of said second transformer and the control winding of said reactor, said network being adjusted in accordance with the adjustment of the voltage divider whose adjusting element affords the highest signal voltage.

6. In combination, a source of single phase output device, and an adjustable phase-shift network comprising a transformer having a primary winding connected to said source and having a secondary winding with two intermediate taps and an overhanging section between one of such taps and one end terminal thereof, a saturable reactor, an adjustable resistor, a capacitor, a second transformer having a primary winding in circuit with said one end terminal of the secondary winding of the first mentioned transformer, the control winding of said reactor and said adjustable resistor and having a secondary winding in circuit with the other intermediate tap of the secondary winding of said first mentioned transformer, the alternating current windings of said reactor, said output device and said capacitor, an adjustable resistor and a capacitor connected in series and together in parallel with the secondary winding of said second transformer, a plurality of half-wave rectifiers and a corresponding number of adjustable voltage dividers each of which has a resistance element connected in parallel with the secondary winding of said first mentioned transformer and an adjusting element connected in series with an associated rectifier to the connection between the primary winding of said second transformer and the control winding of said reactor, said network being adjustable in accordance with the adjustment of the volt- 7 age divider whose adjusting element afiords the highest signal voltage.

7. For supplying and effecting adjustment of the phase angle of a voltage applied to a control circuit, a network comprising a transformer having a primary winding to be supplied from an alternating current source and having a secondary winding having at least one intermediate tap, an adjustable voltage divider having its impedance element connected in parallel with the secondary winding of said transformer, a pair of impedance devices having diflerent impedance characteristics with respect to each other connected in series and together in parallel with a portion of said secondary winding of said transformer, half wave rectifying means, a second transformer having a primary winding in series circuit with said rectifying means between the adjusting element of said voltage divider and the secondary winding of said first mentioned transformer, said second transformer having a secondary winding connected in parallel with one of said impedance devices.

8. The combination of claim 7 in which said impedance device in parallel with the secondary 8,. winding of said second transformer includes resistive impedance and the other of said impedance devices includes inductive impedance.

9. The combination of claim 8 in which said other of said impedance devices comprises a control element of a control circuit.

10. The combination of claim 8 in which said other of said impedance devices comprises a control element of a control circuit and a saturable reactor.

WILLIAM H. ELLIOT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,986,622 Case Jan. 1, 1935 2,005,893 Gulliksen June 25, 1935 2,030,100 Dawson Feb. 11, 1936 2,054,496 Craig Sept. 15, 1936 2,323,427 Slinger July 6, 1943 2,483,090 Fuller Sept. 27, 1949 2,495,158 Carlin Jan. 17, 1950 2,561,080 Van De Weil July 17, 1951 

